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When assessing risks posed by chemical toxicants, risk assessors must estimate a receptor's level of exposure to them in abiotic (soil, water, etc.) and biotic (tissues, prey items) media. However, any free living terrestrial receptor is constantly challenged to avoid or minimize physical and biological stressors. Thus a receptor at a contaminated site may also face challenges from physical and biological, as well as toxicant, stressors. Toxicant stress may pose a risk on its own, or may add to risk posed by physical and biological stressors that are a part of a receptor's everyday existence. It is generally recognized that the relative spatial positions of receptors and contaminated media can strongly influence estimates of exposure and hence of risk. How a receptor moves with respect to habitat directly influences how it may be affected by one or more stressors. This paper was prepared to provoke further discussions on: (1) the benefits associated with attempting to estimate a terrestrial receptor's exposure to multiple stressors as that receptor moves through both space and time and (2) the challenges posed by attempting such an estimate in the context of a typical production ecological risk assessment.
ecological risk, spatially-explicit, bioenergetic, multiple stressors
Senior Environmental Toxicologist, Land Quality Division, Oregon Department of Environmental Quality, Portland, Oregon